Thermactor
Member
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- 541
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- San Diego
oh wonderful
i wonder how feasible it is to put one of those diffs in an LS, I like the idea of low-RPM cruising. But probably the cost of doing so would by far offset any fuel economy gains.
SC400 Vs. LS400 Differential
- Thread starter Lextreme II
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The 1UZFE EGR Delete Kit is available for sale here.
i wonder how feasible it is to put one of those diffs in an LS, I like the idea of low-RPM cruising. But probably the cost of doing so would by far offset any fuel economy gains.
Given the different size of both the ring gear and the differential pumpkin (the 6MT TT differential utilized axles different from the Auto TT accordingly), the swap is likely not viable.
However, the 98-00 SC400 and GS400 came with a 3.26 ratio, which is not light years away from the 3.1 ratio in the Supra 6MT. The 98-00 SC400 and GS400 differential is cross-compatible with both the Supra Auto TT differential and previous SC differential iterations.
I am not certain of the cross-compatibility of the 96 LS400 differential and the SC400 differential (for example). But, assuming they are indeed identical, the 3.26 rear end would be the best for economy.
These units are somewhat highly sought after by the turbo SC/GS guys who are looking for better traction and longer power bands, but they are still able to be had for ~$300-$400: a far cry from the ~$1000 which a 6MT Differential will run.
The 92-97 SC400 has a 3.92 ratio.
The 90-97 SC400 has a 3.62 ratio.
The 93-98 Supra Automatic TT has a 3.77 ratio (3.769)
The 93-98 Supra 6spd manual TT has a 3.13 ratio
The 98+ LS400, SC400 and GS400 have a 3.26 ratio
There is not much difference between Jibbby's SC400 that had a 3.92 and his change to the Supra diff with a 3.77 (4% LESS torque at the wheels)
There will be a slight gain in rwtq for the same change on a 90-97 LS400 with a 3.62 ratio stock going to the 3.77 is a (4% MORE torque at the wheels)
There will be a substantial increase in RWTQ if a 1998+ car make this change going from 3.26 to 3.77 is nearly a 16% increase in RWTQ.
All of the bolts, both on the subframe and the driveshaft companion flange, were a perfect fit: no modifications at all.
I salvaged the differential from CL Member Aliga for $150 shipped off a 97 SC300 a/t with 50k miles, and I rebuilt it to include a Torsen LSD.
I took almost 0.4s off my 45-65mph time from the gearing. Similar results would occur with or without the LSD. It is a great cheap mod.
I actually am getting better economy in the city (where I do most of my driving) since the engine does not have to rev as hard to accelerate at pedestrian speeds going stoplight to stoplight. On the highway, I do have to stay closer to the speed limit (70mph in Indiana and Michigan) to prevent the tach from creeping up near 3k and suffering a big loss in economy.
All in all, it is a cheap mod that really works.
JZA70 is definitely an 8" Torsen LSD; but, the LSD unit is not of the appropriate width dimension to fit in the SC's pumpkin. You need a JZA80 LSD...and, yes, they are tough to come by: be patient.
Even with the 4.27 rear, the stock 149mph fuel cut is the limiting variable and not gearing.
The highway economy is definitely something to consider. I have toned my highway cruising speed down 5-10% to accomodate for the 10% shorter gears. For the extra pep around the city -where I drive normally- I consider the 4.27 gears to be very worthwhile.
The automatic trans has not missed a beat. GS400 guys with the 3.76 Supra TT rear end (+15% vs +10%) are pushing their stock trans much harder than I am. In fact, some of those 3.76 LSD GS400 guys have the RMM supercharger kit. It is my understanding that they make boost on a on a rear end 15% shorter from stock without any issues.
i wonder how feasible it is to put one of those diffs in an LS, I like the idea of low-RPM cruising. But probably the cost of doing so would by far offset any fuel economy gains.
Blizzy
New Member
- Messages
- 91
- Location
- Fort Wayne, IN
Given the different size of both the ring gear and the differential pumpkin (the 6MT TT differential utilized axles different from the Auto TT accordingly), the swap is likely not viable.
However, the 98-00 SC400 and GS400 came with a 3.26 ratio, which is not light years away from the 3.1 ratio in the Supra 6MT. The 98-00 SC400 and GS400 differential is cross-compatible with both the Supra Auto TT differential and previous SC differential iterations.
I am not certain of the cross-compatibility of the 96 LS400 differential and the SC400 differential (for example). But, assuming they are indeed identical, the 3.26 rear end would be the best for economy.
These units are somewhat highly sought after by the turbo SC/GS guys who are looking for better traction and longer power bands, but they are still able to be had for ~$300-$400: a far cry from the ~$1000 which a 6MT Differential will run.
jibbby
New Member
- Messages
- 3,824
- Location
- Santa Monica, California
Fellas, There is hardly a noticeable difference between the open end LS and SC Lexus differentials gearing ratio and the 93-98 Supra TT automatic differential gearing ratio... Speedo is off maybe 5-10 mph on the freeway going 70mph... Like I said you will not even notice the difference..
I am living proof to that as I changed out my differential a few years back to the torsen Supra dif.....Needless to say it was a perfect mate... No regrets, just gained traction...
Hope this little piece of info. helps in your decision making...
I am living proof to that as I changed out my differential a few years back to the torsen Supra dif.....Needless to say it was a perfect mate... No regrets, just gained traction...
Hope this little piece of info. helps in your decision making...
JBrady
Active Member
- Messages
- 1,776
- Location
- Houston Texas
The 92-97 SC400 has a 3.92 ratio.
The 90-97 SC400 has a 3.62 ratio.
The 93-98 Supra Automatic TT has a 3.77 ratio (3.769)
The 93-98 Supra 6spd manual TT has a 3.13 ratio
The 98+ LS400, SC400 and GS400 have a 3.26 ratio
There is not much difference between Jibbby's SC400 that had a 3.92 and his change to the Supra diff with a 3.77 (4% LESS torque at the wheels)
There will be a slight gain in rwtq for the same change on a 90-97 LS400 with a 3.62 ratio stock going to the 3.77 is a (4% MORE torque at the wheels)
There will be a substantial increase in RWTQ if a 1998+ car make this change going from 3.26 to 3.77 is nearly a 16% increase in RWTQ.
jibbby
New Member
- Messages
- 3,824
- Location
- Santa Monica, California
Thank you JBrady...
I didn't know there were variations in gearing ratio's between year Lexus models...
I didn't know there were variations in gearing ratio's between year Lexus models...
Blizzy
New Member
- Messages
- 91
- Location
- Fort Wayne, IN
I went from the 3.92 in my SC400 to a 4.27 rear end from the SC300 a/t, and the ~10% increase in torque is noticeable in every gear.
stevechumo
Active Member
- Messages
- 3,054
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- OC, City of Sunshine
Interesting! I guess this is the way to go and cheap, too. How's the fitment?
Blizzy
New Member
- Messages
- 91
- Location
- Fort Wayne, IN
All of the bolts, both on the subframe and the driveshaft companion flange, were a perfect fit: no modifications at all.
I salvaged the differential from CL Member Aliga for $150 shipped off a 97 SC300 a/t with 50k miles, and I rebuilt it to include a Torsen LSD.
I took almost 0.4s off my 45-65mph time from the gearing. Similar results would occur with or without the LSD. It is a great cheap mod.
I actually am getting better economy in the city (where I do most of my driving) since the engine does not have to rev as hard to accelerate at pedestrian speeds going stoplight to stoplight. On the highway, I do have to stay closer to the speed limit (70mph in Indiana and Michigan) to prevent the tach from creeping up near 3k and suffering a big loss in economy.
All in all, it is a cheap mod that really works.
cokeman
New Member
- Messages
- 3
- Location
- mesa, arizona
This is great info, I hope to put lower gears in my 92 ls400 turbo 4.27:1 sounds like a nice ratio.
www.youtube.com search ls400 turbo
www.youtube.com search ls400 turbo
cokeman
New Member
- Messages
- 3
- Location
- mesa, arizona
I read earlier in this discussion that the 97 sc300 has an axle ratio of 4.27:1 anybody out there know what other years for the sc300 had this same ratio?
lexhere27
New Member
- Messages
- 15
- Location
- Minneapolis, MN USA
Is it possible to use a JZA80 torsen LSD from a TT 6MT with a sc300 pre 98 ring gear to make up Blizzy's set up. Are the ring gears the same size?
Blizzy
New Member
- Messages
- 91
- Location
- Fort Wayne, IN
A 6MT LSD will not work with the SC's ring gear. The SC's ring gear has ten bolts to the 6MT LSD's 12; and, the rings differ in diameter by ~0.4".
You need an Auto TT LSD to work with the SC's ring gear.
You need an Auto TT LSD to work with the SC's ring gear.
lexhere27
New Member
- Messages
- 15
- Location
- Minneapolis, MN USA
Will a 91 JZA70 Torsen LSD work with the pre 98 sc300 with the 4.27 gear ratio? I haven't been able to find the exact measurements but I read it was a 8" or 200mm crown gear that has the 10 bolt configuration. Having a tough time finding the JZA80 8" Torsen LSD:damnit:
jibbby
New Member
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- 3,824
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- Santa Monica, California
Just keep in mind when changing the rear differential gearing to create more torque this will inturn reduce your overall top speed, create higher rpms during normal highway driving which inturn decreases fuel economy...
Just something to consider on the aggressive gearing changes......I also don't know how the automatic transmission shifts will react to big change either....
Just something to consider on the aggressive gearing changes......I also don't know how the automatic transmission shifts will react to big change either....
Blizzy
New Member
- Messages
- 91
- Location
- Fort Wayne, IN
JZA70 is definitely an 8" Torsen LSD; but, the LSD unit is not of the appropriate width dimension to fit in the SC's pumpkin. You need a JZA80 LSD...and, yes, they are tough to come by: be patient.
Blizzy
New Member
- Messages
- 91
- Location
- Fort Wayne, IN
Even with the 4.27 rear, the stock 149mph fuel cut is the limiting variable and not gearing.
The highway economy is definitely something to consider. I have toned my highway cruising speed down 5-10% to accomodate for the 10% shorter gears. For the extra pep around the city -where I drive normally- I consider the 4.27 gears to be very worthwhile.
The automatic trans has not missed a beat. GS400 guys with the 3.76 Supra TT rear end (+15% vs +10%) are pushing their stock trans much harder than I am. In fact, some of those 3.76 LSD GS400 guys have the RMM supercharger kit. It is my understanding that they make boost on a on a rear end 15% shorter from stock without any issues.
fastegg
Member
- Messages
- 432
- Location
- Gosford Australia
Diff ratio's
JBrady states that The 92-97 SC400 has a 3.92 ratio.
The 90-97 SC400 has a 3.62 ratio.
doesn't make sence...... are your years correct ?
PS: I read last night that the Euro Supra JZA80L (2JZGTE 6MT)
has a diff oil cooler as standard... (ide download an image onto this page but i don't know how..
JBrady states that The 92-97 SC400 has a 3.92 ratio.
The 90-97 SC400 has a 3.62 ratio.
doesn't make sence...... are your years correct ?
PS: I read last night that the Euro Supra JZA80L (2JZGTE 6MT)
has a diff oil cooler as standard... (ide download an image onto this page but i don't know how..
